The attorney general's lawsuit was filed in Barry County and includes six counts against Tyson for pollution of state waters and violations of Missouri's hazardous waste laws. Koster said the state's waterways are one of Missouri's most significant natural resources.

"Tyson's conduct threatened the vitality of Clear Creek as a resource for Southwest Missouri," Koster said in a statement. "Tyson Foods must be held accountable for dumping pollution into the waterways of Southwest Missouri, and this conduct must not happen again."

According to the lawsuit, an acidic liquid animal feed supplement called Alimet leaked into the secondary containment and mixed with water around at least one tank in Tyson's feed mill in Aurora. Employees pumped the mixture of water and feed supplement to tanker trucks and moved the liquid to its poultry processing facility in Monett. The lawsuit states some was discharged directly into Monett's city sewer lines and that the remainder was released after Tyson employees had attempted to neutralize its acidity.

Discharges from Tyson interfered with the ability of Monett's sewage system to treat wastewater effectively from at least May 19 to 29. The result was the killing of more than 100,000 fish and other wildlife in a four-mile stretch of Clear Creek, according to the attorney general's office.

Tyson Foods spokesman Dan Fogleman said in a statement the company is sorry about what happened and has started trying to make things right. Tyson is apologizing in newspaper ads, has met with community leaders and has requested to discuss with the Missouri Department of Natural Resources about how it can help improve Clear Creek.

"We've also taken a hard look at how we manage environmental matters at Monett and are improving our processes because we don't want this to ever happen again," Fogleman said.